Control of Granulocyte Production

ABSTRACT In normal conditions the granulocytic cell population is prevented from excessive cell proliferation by a humoral mechanism based on a specific feedback inhibitor, granulocytic chalone. In conditions of acute functional demand a tissue‐specific stimulator, granulocytic antichalone, replaces chalone in rat serum. Mature granulocytes contain, and presumably produce, the chalone which is also present in fresh normal serum. Thus, the inhibitor is both humoral and present within the same cell system on which it acts: the action of this chalone is target tissue specific as it only inhibits granulocytic precursor cells in normal rat bone marrow in vitro. Granulocytic chalone and antichalone were partly purified by gel filtration on Sephadex; the elution parameters suggested molecular weights of 4000 and 30,000–35,000, respectively. Granulocytic chalone was not separated from the erythrocytic chalone (present in fresh normal serum and in blood erythrocytes) on Sephadex; however, separation at the cellular level was easily achieved.